U.S. patent number 10,351,957 [Application Number 14/384,603] was granted by the patent office on 2019-07-16 for method for producing metal oxide film and metal oxide film.
This patent grant is currently assigned to TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION. The grantee listed for this patent is Takahiro Hiramatsu, Hiroyuki Orita, Takahiro Shirahata. Invention is credited to Takahiro Hiramatsu, Hiroyuki Orita, Takahiro Shirahata.
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United States Patent |
10,351,957 |
Shirahata , et al. |
July 16, 2019 |
Method for producing metal oxide film and metal oxide film
Abstract
In a method for producing a metal oxide film according to the
present invention, a solution containing zinc is sprayed onto a
substrate placed under non-vacuum, and then, a dopant solution
containing a dopant is sprayed onto the substrate. After that, a
deposited metal oxide film is subjected to a resistance reducing
treatment. A molar concentration of the dopant supplied to the
substrate with respect to a molar concentration of the zinc
supplied to the substrate is not less than a predetermined
value.
Inventors: |
Shirahata; Takahiro (Tokyo,
JP), Orita; Hiroyuki (Tokyo, JP),
Hiramatsu; Takahiro (Tokyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Shirahata; Takahiro
Orita; Hiroyuki
Hiramatsu; Takahiro |
Tokyo
Tokyo
Tokyo |
N/A
N/A
N/A |
JP
JP
JP |
|
|
Assignee: |
TOSHIBA MITSUBISHI-ELECTRIC
INDUSTRIAL SYSTEMS CORPORATION (Tokyo, JP)
|
Family
ID: |
49258526 |
Appl.
No.: |
14/384,603 |
Filed: |
March 28, 2012 |
PCT
Filed: |
March 28, 2012 |
PCT No.: |
PCT/JP2012/058153 |
371(c)(1),(2),(4) Date: |
September 11, 2014 |
PCT
Pub. No.: |
WO2013/145160 |
PCT
Pub. Date: |
October 03, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150034885 A1 |
Feb 5, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C
18/1291 (20130101); C23C 18/1258 (20130101); C23C
18/1216 (20130101); C23C 18/1295 (20130101); H01B
1/08 (20130101); H01L 31/1884 (20130101); Y02E
10/50 (20130101) |
Current International
Class: |
H01B
1/08 (20060101); C23C 18/12 (20060101); H01L
31/18 (20060101); C23C 18/14 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
102165096 |
|
Aug 2011 |
|
CN |
|
11 2008 004 012 |
|
Sep 2011 |
|
DE |
|
1 264929 |
|
Oct 1989 |
|
JP |
|
9 45140 |
|
Feb 1997 |
|
JP |
|
2005 29408 |
|
Feb 2005 |
|
JP |
|
2011 124330 |
|
Jun 2011 |
|
JP |
|
10-2011-0056522 |
|
May 2011 |
|
KR |
|
201213265 |
|
Apr 2012 |
|
TW |
|
2010 035313 |
|
Apr 2010 |
|
WO |
|
2010 123030 |
|
Oct 2010 |
|
WO |
|
2011 155635 |
|
Dec 2011 |
|
WO |
|
Other References
International Preliminary Report on Patentability and Written
Opinion dated Oct. 9, 2014 in PCT/JP2012/058153 filed on Mar. 28,
2012 (with English Translation). cited by applicant .
Office Action dated Nov. 10, 2015 in Chinese Patent Application No.
201280071728.2 (with English language translation). cited by
applicant .
Office Action dated Dec. 1, 2015 in Japanese Patent Application No.
2014-507128 (with English language translation). cited by applicant
.
Search Report dated May 6, 2015 in Chinese Patent Application No.
2012800717282 (with partial English translation). cited by
applicant .
Office Action dated Aug. 28, 2015 in Korean Patent Application No.
10-2014-7026730 (with Japanese language translation and English
language translation based on Japanese language translation). cited
by applicant .
Office Action dated Jan. 11, 2016 in Korean Patent Application No.
10-2014-7026730 with partial English translation and Japanese
translation. cited by applicant .
J.G. Lu, et a., "Zno-based thin films synthesized by atmospheric
pressure mist chemical vapor deposition", Journal of Crystal
Growth, vol. 299, pp. 1-10, (2007). cited by applicant .
International Search Report dated May 15, 2012 in PCT/JP12/058153
Filed Mar. 28, 2012. cited by applicant .
Taiwanese Search Report dated May 14, 2014 in Taiwanese Application
101119711 May 22, 2014. cited by applicant.
|
Primary Examiner: Young; William D
Attorney, Agent or Firm: Oblon, McClelland, Maier &
Neustadt, L.L.P.
Claims
The invention claimed is:
1. A method for producing metal oxide film, the method comprising:
(A) spraying a solution comprising zinc onto a substrate placed
under non-vacuum; (B) spraying a dopant solution comprising a
dopant onto the substrate, wherein the dopant is at least one of
boron, gallium, indium and aluminum; and (C) performing, on a metal
oxide film deposited on the substrate obtained after said spraying
(A) and said spraying (B), a resistance reducing treatment by
irradiating the metal oxide film with ultraviolet rays that does
not involve rearrangement of crystals of the metal oxide film,
wherein a molar concentration of the dopant supplied to the
substrate in said spraying (B) with respect to a molar
concentration of zinc supplied to the substrate in said spraying is
not less than 0.4% when the dopant is at least one of boron, indium
and aluminum and is not less than 0.33% when the dopant is
gallium.
2. The method according to claim 1, further comprising (D) spraying
an oxidation source onto the substrate in said spraying (A) and
said spraying (B).
3. The method according to claim 2, wherein the solution in said
spraying (A), the oxidation source in said spraying (D), and the
dopant solution in said spraying (B) are supplied to the substrate
through different systems.
4. The method according to claim 1, wherein the dopant is
boron.
5. The method according to claim 1, wherein the dopant is
gallium.
6. The method according to claim 1, wherein the dopant is
indium.
7. The method according to claim 1, wherein the dopant is aluminum.
Description
TECHNICAL FIELD
The present invention relates to a method for producing a metal
oxide film and a metal oxide film and is applicable to a method for
producing a metal oxide film for use in, for example, solar cells
and electronic devices.
BACKGROUND ART
Techniques such as metal organic chemical vapor deposition (MOCVD)
and sputtering that use a vacuum are employed as the method for
depositing a metal oxide film for use in, for example, solar cells
and electronic devices. The metal oxide films produced by those
methods for producing a metal oxide film have excellent film
properties.
For example, a transparent conductive film produced by the
above-mentioned method for producing a metal oxide film has a low
resistance and, if the produced transparent conductive film is
heated, its resistance does not increase.
Patent Literature 1 is an example of the prior literatures
regarding the deposition of a zinc oxide film by the MOCVD
technique. Patent Literature 2 is an example of the prior
literatures regarding the deposition of a zinc oxide film by the
sputtering technique.
CITATION LIST
Patent Literatures
Patent Literature 1: Japanese Patent Application Laid-Open No.
2011-124330
Patent Literature 2: Japanese Patent Application Laid-Open No.
09-45140 (1997)
SUMMARY OF INVENTION
Problems to be Solved by the Invention
Unfortunately, the MOCVD technique requires a high cost in addition
to requiring the use of materials that are unstable in the air,
which makes it less convenient. Also, a plurality of apparatuses
are required in producing a metal oxide film having a laminated
structure by sputtering, which unfortunately increases an apparatus
cost. Therefore, a method for producing a metal oxide film, which
is capable of producing a low-resistance metal oxide film at low
cost, is desired.
The present invention therefore has an object to provide a method
for producing a metal oxide film, which is capable of producing a
low-resistance metal oxide film at low cost. The present invention
has another object to provide a metal oxide film deposited by the
method for producing a metal oxide film.
Means for Solving the Problems
To achieve the above-mentioned objects, a method for producing
metal oxide film according to the present invention includes the
steps of: (A) spraying a solution containing zinc onto a substrate
placed under non-vacuum; (B) spraying a dopant solution containing
a dopant onto the substrate in the step (A); and (C) performing, on
a metal oxide film deposited on the substrate through the step (A)
and the step (B), a resistance reducing treatment that does not
involve rearrangement of crystals of the metal oxide film. In the
steps (A) and (B), a molar concentration of the dopant supplied to
the substrate with respect to a molar concentration of the zinc
supplied to the substrate is not less than a predetermined
value.
Effects of the Invention
The method for producing metal oxide film according to the present
invention includes the steps of: (A) spraying a solution containing
zinc onto a substrate placed under non-vacuum; (B) spraying a
dopant solution containing a dopant onto the substrate in the step
(A); and (C) performing, on a metal oxide film deposited on the
substrate through the step (A) and the step (B), a resistance
reducing treatment that does not involve rearrangement of crystals
of the metal oxide film. In the steps (A) and (B), a molar
concentration of the dopant supplied to the substrate with respect
to a molar concentration of the zinc supplied to the substrate is
not less than a predetermined value.
The method for producing a metal oxide film according to the
present invention performs the deposition process for a metal oxide
film on a substrate under non-vacuum. This reduces the cost of the
deposition process (deposition apparatus cost), which also improves
convenience.
The method for producing a metal oxide film according to the
present invention performs the resistance reducing treatment on a
deposited metal oxide film. Therefore, even in a case where a metal
oxide film is deposited on a substrate under non-vacuum, the
resistance of the metal oxide film can be reduced (the resistance
of a metal oxide film deposited under non-vacuum can be reduced to
be substantially equal to the resistance of a metal oxide film
deposited under vacuum).
The method for producing a metal oxide film according to the
present invention further supplies (sprays) zinc and a dopant onto
a substrate, to thereby deposit a metal oxide film on the
substrate. When zinc and a dopant are supplied onto the substrate,
a (dopant)/Zn molar concentration ratio is set to be not less than
a predetermined value. This allows for suppressing an increase in
the resistance of a metal oxide film subjected to the resistance
reducing treatment after a lapse of a long period of time from the
resistance reducing treatment.
The object, features, aspects and advantages of the present
invention will become more apparent from the following detailed
description and the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 A configuration diagram of a deposition apparatus for
describing a method for depositing a metal oxide film according to
the present invention.
FIG. 2 A diagram for describing a method for producing a metal
oxide film (in particular, a resistance reducing treatment)
according to the present invention.
FIG. 3 A diagram showing variations over time of the resistivities
of metal oxide films deposited by the method for producing a metal
oxide film according to the present invention.
FIG. 4 A diagram showing deposition conditions of the metal oxide
films.
FIG. 5 A diagram showing variations over time of the resistivities
of metal oxide films deposited by the method for producing a metal
oxide film according to the present invention.
FIG. 6 A diagram showing deposition conditions of the metal oxide
films.
FIG. 7 A diagram showing variations over time of the resistivities
of metal oxide films deposited by the method for producing a metal
oxide film according to the present invention.
FIG. 8 A diagram showing deposition conditions of the metal oxide
films.
DESCRIPTION OF EMBODIMENT
A method for producing a metal oxide film according to the present
invention performs a deposition process under non-vacuum (at
atmospheric pressure). Herein, a metal oxide film containing zinc
(Zn) deposited under non-vacuum (at atmospheric pressure) has high
resistance after deposition. For this reason, the metal oxide film
immediately after deposition is subjected to a resistance reducing
treatment that does not involve a high-temperature treatment (that
is, the metal oxide film immediately after deposition is subjected
to the resistance reducing treatment to provide energy of a bandgap
or more of a metal oxide film, the process not involving crystal
reconfiguration of a metal oxide film). For example, ultraviolet
irradiation for a metal oxide film is adoptable as the resistance
reducing treatment.
The resistance reducing treatment can reduce the resistance of a
metal oxide film immediately after the resistance reducing
treatment.
The inventors have found that the resistance of a metal oxide film
containing no dopant (undoped metal oxide film) increases again
after a lapse of time from the resistance reducing treatment.
Also, the inventors have found that when a dopant and zinc are
supplied to a substrate, a molar concentration of the dopant to be
supplied to the substrate with respect to the molar concentration
of the zinc to be supplied to the substrate is set to be not less
than a predetermined value (in other words, with a lower limit set
to a molar concentration ratio of a dopant with respect to zinc to
be supplied to the substrate, a dopant of this molar concentration
of the lower limit or more is supplied to the substrate),
suppressing an increase in the resistance of the metal oxide film
even after a lapse of time from the resistance reducing
treatment.
The present invention will be specifically described below with
reference to the drawings showing an embodiment thereof.
<Embodiment>
The method for producing a metal oxide film according to this
embodiment will be specifically described with the use of a
production apparatus (deposition apparatus) shown in FIG. 1.
First, a solution 7 containing at least zinc is produced. Herein,
an organic solvent such as ether or alcohol is used as a solvent of
the solution 7. The produced solution 7 is filled into a container
3A as shown in FIG. 1.
Water (H.sub.2O) is used as an oxidation source 6 and, as shown in
FIG. 1, the oxidation source 6 is filled into a container 3B. While
oxygen, ozone, hydrogen peroxide, N.sub.2O, NO.sub.2, and the like
can be used as the oxidation source 6 in addition to water, water
is desirably used in terms of inexpensive cost and easy handling
(the oxidation source 6 is water in the following description).
Also, a dopant solution 5 containing a dopant is produced. For
example, the dopant solution 5 containing boron (B) is produced.
Usable as the dopant solution 5 is, for example, a boric acid
(H.sub.3BO.sub.3) solution. The produced dopant solution 5 is
filled into a container 3C as shown in FIG. 1.
Next, the solution 5, the oxidation source 6, and the solution 7
are individually formed into mist. The container 3A is provided
with an atomizer 4A on the bottom thereof, the container 3B is
provided with an atomizer 4B on the bottom thereof, and the
container 3C is provided with an atomizer 4C on the bottom thereof.
The atomizer 4A forms the solution 7 in the container 3A into mist,
the atomizer 4B forms the oxidation source 6 in the container 3B
into mist, and the atomizer 4C forms the dopant solution 5 in the
container 3C into mist.
The misted solution 7 passes through a path L1 to be supplied to a
nozzle 8, the misted oxidation source 6 passes through a path L2 to
be supplied to the nozzle 8, and the misted dopant solution 5
passes through a path L3 to be supplied to the nozzle 8. As shown
in FIG. 1, herein, the path L1, the path L2, and the path L3 are
different paths.
It is necessary in the present invention that a molar concentration
of a dopant to be supplied to a substrate 1 with respect to a molar
concentration of zinc to be supplied to the substrate 1 (that is, a
dopant/Zn molar concentration ratio) be larger than or equal to a
predetermined value. The molar concentration ratio is adjustable by
adjusting a carrier gas amount (liter/min) of the solution 7 to be
supplied to the nozzle 8 (or the substrate 1), a molar
concentration of zinc in the solution 7, a carrier gas amount
(liter/min) of the dopant solution 5 to be supplied to the nozzle 8
(or the substrate 1), and a molar concentration of a dopant in the
dopant solution 5.
As shown in FIG. 1, the substrate 1 is placed on a heating unit 2.
Herein, the substrate 1 is placed under non-vacuum (at atmospheric
pressure). The misted solution 7, the misted oxidation source 6,
and the misted dopant solution 5 are sprayed onto the substrate 1
placed under non-vacuum (at atmospheric pressure) from discrete
exhaust ports by means of the nozzle 8. In this spraying, the
substrate 1 is heated to, for example, about 200.degree. C. on the
heating unit 2.
The above-mentioned process deposits a metal oxide film (zinc oxide
film being a transparent conductive film) having a predetermined
film thickness on the substrate 1 placed under non-vacuum (at
atmospheric pressure). As apparent from the above-mentioned
process, in the present invention, the deposited metal oxide film
contains zinc, and further, zinc contains a dopant.
The metal oxide film deposited under non-vacuum (at atmospheric
pressure) has a resistance higher than that of the metal oxide film
deposited under vacuum, such as through sputtering. Thus, the
method for producing a metal oxide film according to the present
invention performs the resistance reducing treatment to provide
energy of not less than a bandgap of a metal oxide film, the
process not involving rearrangement of crystals of a metal oxide
film.
For example, as shown in FIG. 2, the method for producing a metal
oxide film according to this embodiment irradiates the entire main
surface of the metal oxide film 10 deposited on the substrate 1
with ultraviolet rays 13 using an ultraviolet lamp 12 or the like.
The irradiation of the ultraviolet rays 13 can reduce a resistance
(resistivity) of the metal oxide film 10.
If a metal oxide film is, for example, an undoped film as described
above, a resistance thereof increases after a lapse of time even by
performing the resistance reducing treatment on the deposited metal
oxide film. This results in that the resistance of the metal oxide
film returns to a resistance value prior to the resistance reducing
treatment.
Meanwhile, if the metal oxide film contains a dopant and a
dopant/Zn molar concentration ratio in supply of a dopant and zinc
to the substrate 1 is not less than a predetermined value, the
metal oxide film is subjected to the resistance reducing treatment,
suppressing an increase in the resistance of the metal oxide film
after a lapse of time from the resistance reducing treatment.
FIG. 3 shows experimental data on an effect of suppressing a
resistance increase as described above. FIG. 3 shows variations
over time of the resistivity of each metal oxide film. To be more
specific, FIG. 3 shows variations over time of the resistivity of
each metal oxide film during irradiation of ultraviolet rays
(resistance reducing treatment) and after the irradiation of
ultraviolet rays. The vertical axis and horizontal axis of FIG. 3
indicate resistivity (.OMEGA.cm) and time (h), respectively.
For the experimental data shown in FIG. 3, the measurement targets
are an undoped metal oxide film containing zinc and a plurality of
metal oxide films containing a dopant and zinc. Herein, the dopant
is boron. FIG. 3 shows, as a plurality of metal oxide films
containing a dopant and zinc, a metal oxide film having a B/Zn
molar concentration ratio of 0.2% when zinc and boron were supplied
to the substrate 1, a metal oxide film having a B/Zn molar
concentration ratio of 0.4% when zinc and boron were supplied to
the substrate 1, a metal oxide film having a B/Zn molar
concentration ratio of 0.8% when zinc and boron were supplied to
the substrate 1, and a metal oxide film having a B/Zn molar
concentration ratio of 1.8% when zinc and boron were supplied to
the substrate 1.
Herein, the temperature for depositing all the metal oxide films is
200.degree. C. Each metal oxide film is deposited in the deposition
apparatus shown in FIG. 1, and the deposition conditions are as
shown in FIG. 4.
As shown in FIG. 4, for an undoped metal oxide film, an amount of
zinc supplied to the substrate 1 is 1.26 m (milli) mol/min, and an
amount of an oxidizing agent (water) supplied to the substrate 1 is
67 mmol/min.
As shown in FIG. 4, for the metal oxide films respectively having
B/Zn molar concentration ratios of 0.2%, 0.4%, 0.8%, and 1.8%, an
amount of zinc supplied to the substrate 1 is 1.05 mmol/min, and an
amount of an oxidizing agent (water) supplied to the substrate 1 is
67 mmol/min.
As shown in FIG. 3, the resistivity of each metal oxide film has
decreased through irradiation of ultraviolet rays (resistance
reducing treatment). As shown in FIG. 3, however, for the undoped
metal oxide film and the metal oxide film having a B/Zn molar
concentration ratio of 0.2%, the resistivities of the metal oxide
films have increased up to the level prior to the irradiation of
ultraviolet rays (resistance reducing treatment) after a lapse of
time from the end of the irradiation of ultraviolet rays
(resistance reducing treatment).
Meanwhile, for the metal oxide films respectively having the B/Zn
molar concentration ratios of 0.4%, 0.8%, and 1.8%, an increase in
the resistance of the metal oxide film has been suppressed and a
low-resistivity condition has been kept even after a lapse of time
from the end of the irradiation of ultraviolet rays (resistance
reducing treatment) (the resistances of the metal oxide films
containing boron as a dopant have increased very little even after
a lapse of time, and resistance values at the end of the resistance
reducing treatment have remained nearly unchanged).
In a case where the metal oxide film contains boron as a dopant and
a B/Zn molar concentration ratio when zinc and boron are supplied
to the substrate 1 is not less than 0.4%, an increase in the
resistance of the metal oxide film can be suppressed even after a
lapse of time from the resistance reducing treatment performed on
the metal oxide film.
FIG. 5 shows another experimental data on an effect of suppressing
a resistance increase. FIG. 5 shows variations over time of the
resistivity of each metal oxide film. To be more specific, FIG. 5
shows variations over time of the resistivity of each metal oxide
film during irradiation of ultraviolet rays (resistance reducing
treatment) and after the irradiation of ultraviolet rays. The
vertical axis and horizontal axis of FIG. 5 indicate resistivity
(.OMEGA.cm) and time (h), respectively.
For the experimental data shown in FIG. 5, the measurement targets
are an undoped metal oxide film containing zinc and a plurality of
metal oxide films containing a dopant and zinc. Herein, a dopant is
indium (In). FIG. 5 shows, as a plurality of metal oxide films
containing a dopant and zinc, a metal oxide film having an In/Zn
molar concentration ratio of 0.4% when zinc and indium were
supplied to the substrate 1, a metal oxide film having an In/Zn
molar concentration ratio of 0.8% when zinc and indium were
supplied to the substrate 1, and a metal oxide film having an In/Zn
molar concentration ratio of 2.0% when zinc and indium were
supplied to the substrate 1.
Herein, the temperature for depositing all the metal oxide films is
200.degree. C. Each metal oxide film is deposited in the deposition
apparatus shown in FIG. 1, and the deposition conditions are as
shown in FIG. 6.
As shown in FIG. 6, the amount of zinc supplied to the substrate 1
is 0.53 mmol/min for the metal oxide films respectively having
In/Zn molar concentration ratios of 0.4%, 0.8%, and 2.0%, and the
amount of an oxidizing agent (water) supplied to the substrate 1 is
67 mmol/min. The deposition conditions of the undoped metal oxide
film shown in FIG. 6 are identical to the deposition conditions of
the other undoped metal oxide film shown in FIG. 4.
As shown in FIG. 5, the resistivity of each metal oxide film has
decreased through irradiation of ultraviolet rays (resistance
reducing treatment). As shown in FIG. 5, however, for the metal
oxide film being an undoped film, the resistivity of this metal
oxide film has increased up to the level prior to the irradiation
of ultraviolet rays (resistance reducing treatment) after a lapse
of time from the end of the irradiation of ultraviolet rays
(resistance reducing treatment).
Meanwhile, for the metal oxide films respectively having In/Zn
molar concentration ratios of 0.4%, 0.8%, and 2.0%, an increase in
the resistance of the metal oxide film has been suppressed and a
low-resistivity condition has been kept even after a lapse of time
from the end of the irradiation of ultraviolet rays (resistance
reducing treatment) (the resistance of the metal oxide film
containing indium as a dopant has increased a little compared with
the metal oxide film containing boron as a dopant, but
nevertheless, an increase in the resistance of the metal oxide film
containing indium as a dopant has been suppressed
sufficiently).
In a case where the metal oxide film contains indium as a dopant
and an In/Zn molar concentration ratio when zinc and indium are
supplied to the substrate 1 is not less than 0.4%, an increase in
the resistance of the metal oxide film can be suppressed even after
a lapse of time from the resistance reducing treatment performed on
the metal oxide film.
FIG. 7 shows another experimental data on an effect of suppressing
a resistance increase. FIG. 7 shows variations over time of the
resistivity of each metal oxide film. To be more specific, FIG. 7
shows variations over time of the resistivity of each metal oxide
film during irradiation of ultraviolet rays (resistance reducing
treatment) and after the irradiation of ultraviolet rays. The
vertical axis and horizontal axis of FIG. 7 indicate resistivity
(.OMEGA.cm) and time (h), respectively.
For the experimental data shown in FIG. 7, the measurement targets
are an undoped metal oxide film containing zinc and a plurality of
metal oxide films containing a dopant and zinc. Herein, the dopant
is gallium (Ga). FIG. 7 shows, as a plurality of metal oxide films
containing a dopant and zinc, a metal oxide film having a Ga/Zn
molar concentration ratio of 0.33% when zinc and gallium were
supplied to the substrate 1, a metal oxide film having a Ga/Zn
molar concentration ratio of 0.5% when zinc and gallium were
supplied to the substrate 1, a metal oxide film having a Ga/Zn
molar concentration ratio of 0.67% when zinc and gallium were
supplied to the substrate 1, a metal oxide film having a Ga/Zn
molar concentration ratio of 0.83% when zinc and gallium were
supplied to the substrate 1, a metal oxide film having a Ga/Zn
molar concentration ratio of 1.17% when zinc and gallium were
supplied to the substrate 1, and a metal oxide film having a Ga/Zn
molar concentration ratio of 2.67% when zinc and gallium were
supplied to the substrate 1.
Herein, the temperature for depositing all the metal oxide films is
200.degree. C. Each metal oxide film is deposited in the deposition
apparatus shown in FIG. 1, and the deposition conditions are as
shown in FIG. 8.
As shown in FIG. 8, the amount of zinc supplied to the substrate 1
is 1.26 mmol/min for the metal oxide films respectively having
Ga/Zn molar concentration ratios of 0.33%, 0.5%, 0.67%, 0.83%, and
1.17%, and the amount of an oxidizing agent (water) supplied to the
substrate 1 is 67 mmol/min.
The amount of zinc supplied to the substrate 1 is 0.63 mmol/min for
the metal oxide film having a Ga/Zn molar concentration ratio of
2.67%, and the amount of an oxidizing agent (water) supplied to the
substrate 1 is 67 mmol/min.
The deposition conditions of the undoped metal oxide film shown in
FIG. 8 are identical to the deposition conditions of the other
undoped metal oxide film shown in FIG. 4.
As shown in FIG. 7, the resistivity of each metal oxide film has
decreased through irradiation of ultraviolet rays (resistance
reducing treatment). As shown in FIG. 7, however, for the metal
oxide film being an undoped film, the resistivity of this metal
oxide film has increased up to the level prior to the irradiation
of ultraviolet rays (resistance reducing treatment) after a lapse
of time from the end of the irradiation of ultraviolet rays
(resistance reducing treatment).
Meanwhile, for the metal oxide films respectively having Ga/Zn
molar concentration ratios of 0.33%, 0.5%, 0.67%, 0.83%, 1.17%, and
2.67%, an increase in the resistance of the metal oxide film has
been suppressed even after a lapse of time from the end of the
irradiation of ultraviolet rays (resistance reducing treatment)
(the resistance of the metal oxide film containing Ga as a dopant
has increased compared with the metal oxide films containing B and
In as dopants, but nevertheless, an increase in the resistance of
the metal oxide film containing Ga as a dopant has been
suppressed).
In a case where the metal oxide film contains gallium as a dopant
and a Ga/Zn molar concentration ratio when zinc and gallium are
supplied to the substrate 1 is not less than 0.33%, an increase in
the resistance of the metal oxide film can be suppressed even after
a lapse of time from the resistance reducing treatment performed on
the metal oxide film.
Aluminum (Al) is included in the same Group 13 elements as boron,
indium, and gallium, and aluminum also has the same electronic
structure as those of boron, indium, and gallium. Thus, also when a
metal oxide film that contains aluminum as a dopant and contains
zinc is deposited, the deposited metal oxide film behaves similarly
to metal oxide films that contain zinc and, as a dopant, B, In, and
Ga.
As can be seen from the consideration of FIGS. 3, 5, and 7, if a (B
or In or Ga)/Zn molar concentration ratio when zinc and a dopant
(B, In, Ga) are supplied to the substrate 1 is at least 0.4% or
more, an increase in the resistance of the metal oxide film
deposited through the above-mentioned supply can be suppressed
after the resistance reducing treatment. Thus, also in a case where
Al belonging to the same Group 13 as B, In, and Ga is adopted as a
dopant and a metal oxide film containing zinc is deposited, if an
Al/Zn molar concentration ratio when zinc and Al are supplied to
the substrate 1 is at least 0.4% or more, an increase in the
resistance of a metal oxide film to be deposited through the supply
can be suppressed after the resistance reducing treatment.
The method for producing a metal oxide film according to this
embodiment performs the process of depositing a metal oxide film on
the substrate 1 under non-vacuum. This reduces a cost for the
deposition process (deposition apparatus cost) and also improves
convenience.
The method for producing a metal oxide film according to this
embodiment also performs the resistance reducing treatment on a
metal oxide film immediately after deposition. Therefore, if a
metal oxide film is deposited on the substrate 1 under non-vacuum,
the resistance of the metal oxide film can be reduced (the
resistance of the metal oxide film deposited under non-vacuum can
be reduced to be substantially equal to the resistance of a metal
oxide film deposited under vacuum).
The method for producing a metal oxide film according to this
embodiment further supplies (sprays) zinc and a dopant onto the
substrate 1, to thereby deposit a metal oxide film on the substrate
1. Herein, the (dopant)/Zn molar concentration ratio is set to be
not less than a predetermined value when zinc and a dopant are
supplied to the substrate 1. For example, the (B or In or Al)/Zn
molar concentration ratio is at least 0.4% or more, and the Ga/Zn
molar concentration ratio is at least 0.33% or more.
Thus, the method for producing a metal oxide film according to the
present invention can suppress an increase in the resistance of the
metal oxide film subjected to the resistance reducing treatment
even after a lapse of a long period of time from the end of the
resistance reducing treatment.
The method for producing a metal oxide film according to this
embodiment adopts the Group 13 element (boron, aluminum, gallium,
indium) as a dopant of the metal oxide film in the deposition of a
metal oxide film containing zinc. This allows a larger amount of
current to flow through the metal oxide film to be deposited.
As can be seen from the comparison of FIGS. 3, 5, and 7, in the
case where boron is adopted as a dopant, an increase in the
resistance of a metal oxide film after the resistance reducing
treatment can be suppressed most (the resistance value of a metal
oxide film immediately after the resistance reducing treatment can
be maintained even after a lapse of a long period of time). Boron
(boric acid), which is stable and inexpensive, can further reduce a
cost for depositing a metal oxide film and further improve the
convenience of the method for producing a metal oxide film.
The deposition apparatus illustrated in FIG. 1 includes the
container 3A for the solution 7, the container 3B for the oxidation
source 6, and the container 3C for the dopant solution 5 that are
independently provided. Alternatively, any of the containers 3A,
3B, and 3C can be omitted.
For example, the following configurations are adoptable: the
solution 7 and the oxidation source 6 are put in the same one of
the containers and the dopant solution 5 is put in the other
container; the dopant solution 5 and the oxidation source 6 are put
in the same one of the containers and the solution 7 is put in the
other container; and the solution 7 and the dopant solution 5 are
put in the same one of the containers and the oxidation source 6 is
put in the other container.
Whether a container is provided for each of the solutions 5, 6, and
7 or a container is used in common for two solutions can be
selected depending on the types of the dopant solution 7, the
oxidation source 6, and the solution 5 (as an example, depending on
the dopant solubility and the reactivity of each of the solutions
5, 6, and 7).
For example, boric acid is soluble in water, and thus, boric acid
being the dopant solution 5 and water being the oxidation source 6
can be put in the same container.
As described above, the present invention needs to adjust a
(dopant/Zn) molar concentration ratio to be not less than a
predetermined value in a case where zinc and a dopant are supplied
to the substrate 1. Herein, a molar concentration of an element to
be supplied to the substrate 1 is most easily adjusted with the
configuration in which the containers 3A, 3B, and 3C are
individually provided for the solutions 5, 6, and 7 and the
solutions 5, 6, and 7 are supplied to the substrate 1 through the
different systems L1, L2, and L3, respectively.
The deposition process is performed under non-vacuum (at
atmospheric pressure) in the present invention, allowing for the
use of atmospheric oxygen as an oxidation source. Adoption of the
configuration in which the oxidation source 6 is actively supplied
to the substrate 1, as illustrated in FIG. 1, increases the
deposition rate of a metal oxide film and also allows for
deposition of a metal oxide film having good film quality.
The present invention has been described in detail, but the
above-mentioned description is illustrative in all aspects and the
present invention is not intended to be limited thereto. Various
modifications not exemplified are construed to be made without
departing from the scope of the present invention.
DESCRIPTION OF REFERENCE SIGNS
1 substrate
2 heating unit
3A, 3B, 3C container
4A, 4B, 4C atomizer
5 dopant solution
6 oxidation source
7 solution
8 nozzle
10 metal oxide film (transparent conductive film, zinc oxide
film)
12 ultraviolet lamp
13 ultraviolet rays
L1, L2, L3 path
* * * * *